Analyte detection is becoming increasingly important as a security and safety measure. Transportation, commercial, government, educational, and other facilities have a need for the sensitive and rapid detection of analytes, including those that are indicative of explosives or other substances that pose a threat. In addition, in industrial, residential, and commercial settings, analyte detection can provide warning of particles that pose a health or safety risk. Example analytes to be detected include, as nonlimiting examples, hazardous materials, including explosive-related materials, toxic industrial chemicals (TICS), narcotics, and chemical or biological agents, though other analytes may also be detected.
Analysis instruments, such as but not limited to detectors, have been developed and remain under development for detection of analytes. A nonlimiting example analysis instrument currently used in portable and larger forms is the Ion Mobility Spectrometer (IMS), such as the GE VaporTrace models. A typical IMS device has separate particle and vapor modes. In particle mode, an assembly is affixed to the device to accept and desorb particles from a substrate such as a swab during baggage screening. The swab is inserted into the assembly and is heated to desorb any collected particulates, and the particulates are directed via vacuum into the instrument for analysis. This assembly or a different assembly can be affixed to the device for vapor mode, in which the device collects vapors for analyte detection. As one nonlimiting example application, vapor mode is often used to sample contained areas such as automobile trunks at the entrances to military facilities.
Speed and sensitivity are primary concerns for researchers and manufacturers when using analysis instruments, and devices such as preconcentrators can provide improvements for both. Preconcentrators offer the opportunity to enhance the performance of any type of analysis instrument by increasing the concentration of analyte in a volume of fluid sent for analysis. Generally, preconcentrators collect analyte over a period of time during absorption, and then provide a concentrated fluid stream to the analysis device during desorption.
Desorption preferably uses rapid heating. Microscale preconcentrators provide advantages regarding thermal cycling and desorption, particularly that heating for accomplishing desorption can be conducted quickly and with low power. Examples of microscale preconcentrators are disclosed in Manginell et al., U.S. Pat. No. 6,527,835, entitled Chemical Preconcentrator with Integral Thermal Flow Sensor, and in Manginell et al., U.S. Pat. No. 6,171,378, entitled Chemical Preconcentrator.
Example chemical preconcentrators may be formed from a substrate having a suspended membrane, such as low-stress silicon nitride, and incorporate a flow over design. Other successful microscale preconcentrators with a flow through design are disclosed in U.S. Patent Application Publication No. 20050095722 (incorporated by reference herein), published May 5, 2005, and entitled “Microscale Flow Through Sorbent Plate Collection Device”, and in U.S. Patent Application Publication No. 20050226778, published Oct. 13, 2005, and entitled “Microscale Flow Through Sorbent Plate Collection Device” (also incorporated by reference herein). The flow through design can increase contact between the analyte fluid flow and the sorbent in the collection area compared to typical flow over designs that would require creating a turbulent flow to match the level of analyte fluid-sorbent contact.
Another example preconcentrator design provided by some of the inventors of the present application is provided in U.S. Patent Application Publication No. 2009/0249958, application Ser. No. 12/337,449, which is incorporated in its entirety by reference herein.